A device for spraying an electrified powdered material onto a structure

ABSTRACT

Device for spraying an electrified powdered treating or coating material onto a structure. The device comprises a cabin through which the structure is conveyed. A mixture of the powdered material and air is sprayed onto the structure by spraying means connected to metering and mixing means placed in the bottom of a bank containing the powdered material. Means are provided for recovering the powdered material which has not been deposited on the structure and returning this material to the tank.

United States Patent 1 Pierson Feb. 13, 1973 [54] A DEVICE FOR SPRAYINGAN ELECTRIFIED POWDERED MATERIAL ONTO A STRUCTURE [75] lnventor: GeraldPierre Pierson, Calvados,

France [73] Assignee: Societe Carrier, societe anonyme,

Suresnes, France 22 Filed: Oct. 27, 1970 21 Appl. No.: 84,260

[30] Foreign Application Priority Data Nov. 4, 1969 France ..6937914[52] US. Cl. ..118/630, 117/93.41, 117/102, 118/602, 118/621, 118/629[51] Int. Cl. ..B05b 5/02, B05C 11/00 [58] Field of Search ..118/602,621, 623, 626, 627, 118/629, 630, 631, 639, 640; 117/93.41,

[56] References Cited UNITED STATES PATENTS 3,486,921 12/1969 Wallis..117/24 3,539,381 11/1970 Kayarian ..117/102 3,027,870 4/1962 Schirmerm....118/504 3,396,699 8/1968 Beebe et al..... 1 18/634 3,001,719 9/1961Sigvardsson.... ..239/15 2,794,417 6/1957 Starkey et a1... ..118/512,698,814 1/1955 Ransburg ....118/63O 3,434,758 3/1969 Fry ..302/612,706,964 4/1955 Ransburg et a1 ..118/51 3,205,853 9/1965 Wampler et a1...118/631 Primary Examiner-Merviri Stein Assistant ExaminerLeo MillsteinAttorney-Imirie and Smiley [5 7] ABSTRACT Device for spraying anelectrified powdered treating or coating material onto a structure. Thedevice comprises a cabin through which the structure is conveyed. Amixture of the powdered material and air is sprayed onto the structureby spraying means connected to metering and mixing means placed in thebottom of a bank containing the powdered material. Means are providedfor recovering the powdered material which has not been deposited on thestructure and returning this material to the tank.

1 1 Claims, 6 Drawing Figures PATENTEDFEB 13 1975 SHEET 10F 4 FielINVENTAR GERALD P. Pl ERSON I At fs.

PATENTEDFEB 13 I975 SHEET 2 OF 4 'Irll IIIVIII 111 ruvnrron P. PIEQSONGERALD PATENTEUFEB13|973 v 3.716.024 SHEET 30F 4 Pie/1.4. Fiab.

I NVE NTo R GERALD P, PIERSoN PATENTEUFEB 13 I975 3.716(024 SHEET MOF 4INvENToR GERA D P. PI ERSON Att'u.

DEVICE FOR SPRAYING AN ELECTRIFIED POWDERED MATERIAL ONTO A STRUCTURE inmany fields, it is useful or necessary to submit component parts orvarious products, at some stage of their manufacture, production orrealization, to a coating or surface treatment, in order to impartthereto particular appearance characteristics or well determinedproperties, for example, a higher resistance to oxidizing agents withwhich the parts or products may come in contact.

To produce the coating or surface treatments, there are mostly employedliquid products having a variable fraction of solvent, the nature andthe quantity of which depend on the natural or forced drying processesemployed. The surfaces of parts are usually treated or coated by meansofa brush or a roller, or by spraying or dipping.

ln any case, more or less complex but always expen sive treatinginstallations must be designed to prevent, as far as possible, theemanation of products which are generally poisonous'to the personnel incharge of the supervision, maintenance or feeding of material to saidinstallations.

Moreover, notwithstanding the fact that methods such as spraying ordipping have been considerably improved, these methods always entail anexcessive consumption of treating or coating product, which issubsequently very difficult to recover.

Further, when the parts must be transferred to a drying or a bakingenclosure, it will be understood that it is extremely important to takeevery precaution to avoid the sticking of particles, dust or otherforeign elements in suspension in the environment to the still-wetcoatings.

Consequently, it is generally necessary to create transfer passages ortunnels which are usually kept at a relative pressure with respect tothe surroundings while the treating enclosure with which theycommunicate has a relative depression prevailing therein so as to avoidthe emanation of poisonous products. Consequently, the devices arecomplex and expensive and the cost is practically always out ofproportion to the treating possibilities or the importance of the partsor structures to be treated.

An object of the present invention is to remedy the above-mentioneddrawbacks by providing a new device for coating or treating the surfacesof structures or parts whereby it is possible to reduce to a minimum thequantity of treating product utilized, and preclude risks ofevaporationor emanation of this product even when the parts undertreatment must be transferred from the spraying device to a cooling,drying or baking enclosure.

The invention provides a device for spraying electrified powderedmaterial for coating or treating the surface of parts or structurescomprising a cabin having an interior kept at a pressure lower than thesurrounding pressure, some sides of the cabin having lock-chambers forthe passage of a conveyor for moving the parts or products, wherein'theparts are made to pass in front of at least one spray distributor forspraying an airpowder mixture, the particles of said mixture beingsubjected to an electrostatic charge different from the charge of theparts, the effective part of the distributor being provided with anelement dividing up the airpowder mixture flowing therein, thedistributor being in communication with an adjustable metering andmixting means which is supplied with compressed air and disposed in asupply tank containing the powdered material and connected to the lowerpart of said cabin by devices for the recovery of excess powderedmaterial projected.

Various other characteristics of the invention are revealed by thefollowing detailed description.

Embodiments of the invention are shown by way of example in theaccompanying drawings, in which:

FIG. lis a diagrammatic sectional perspective view, partly in section,of the device of the invention HQ 2 is a partial, perspective, enlargedview, partly in section of one of the elements of the device FIG. 3 is asection on a reduced scale of a modification of the device of FIG. 1

FIG. 4 is a sectional view of a modification of the element of FIG. 2;

FIG. 5 is a side elevational view of another modification of the elementof FIG. 2

FIG. 6 is a perspective view, partly cut-away, illustrating anotherembodiment of one of the components of the device.

In FIG. 1, the device comprises a cabin 1 having two opposite openings 2made in the same way as air lockchambers. The openings 2 allow a path ofmovement 3 to extend through the cabin, the path comprising a conveyorextending from a loading station, through the cabin l and leading to anatural or forced drying enclosure.

The cabin 1 is provided at its base with a container 4 containing asupply 5 of powdered product of small grain size, the maximum or optimumlevel of the product being diagrammatically shown in dash-dot line. Thecontainer 4 includes a flat bottom 6 joined to two panels 7 upwardlydiverging from the bottom 6 to corresponding lateral sides of the cabinto constitute product recovering or collecting means. The container 4supports, by means of fixed cross-bars 8, a metering and mixing means 9made of a tubular element 10, similar to the tapered part of a venturi,the small section end 11 thereof being spaced from the bottom 6. Thelarge section portion 12 of the tubular element 10 is combined with apivotable shutter 13 whereby the section of the tubular element 10 canbe regulated. The shutter 13 is connected to a control rod 14 providedwith a control handle 15.

The substantially middle portion of tube 10 communicates with apressurized air injecting pipe 16. The tubular element 10 communicateswith a tube 17 diametrically opposed to the pipe 16 and leading to aspray distributor 18 which extends vertically inside the cabin 1.Depending on the shape of the parts or structures to be treated, thespray distributor 18 can be rectilinear, bent or have some other shape.The distributor 18 is maintained parallel with the wall alongside whichit extends by spacer member 19.

The wall of the distributor 18 has throughout the effective lengththereof an axially extending slot 20 through which extends a strip 21preferably of insulating material and extending transversely acrosssubstantially the whole of the inside section of the distributor 18.This strip 21 has notches 22 and 23 on the two wide faces of the strip,said notches having a constant spacing, but being disposed inalternating staggered relation on the two faces of the strip. Thenotches 22 and 23 can have a uniform shape throughout the width of thestrip 21 or can taper from the edge 24 of the strip facing the inside ofthe cabin l to nothing on the corresponding wide faces of the strip. Thestrip 21 is preferably interchangeable to allow a modification of thespraying characteristics of the distributor 18 in accordance with thenature of powdered product 5 and the work to be performed. The strip 21extends between two fixed or adjustable supports 25, mounted on thedistributor 18 to hold a metallic wire 26 taut in front of the edge 24of the strip 21. The wire 26 is connected to two conductors 27 and 38leading from a high-frequency electric power generator 29.

The above-described device operates in the following way After fillingthe container 4 with a powdered product, the compressed air supplied bythe pipe 16 passes through the metering and mixing means 9 beforereaching the tube 17. The suction which is created inside the tubularelement 10, the magnitude of which can be regulated by controlling theposition of the shutter 13, draws inadditional air and the powderedproduct which is drawn along at a constant flow in the tube 17. Thelatter constitutes a chamber for both metering and homogeneizing themixture of air and powdered product caused to flow through thedistributor 18, the volume of which ensures the expansion of themixture.

Inside the spray distributor 18, the air-powered product mixture flowsthrough the notches 22 and 23 and is divided into as many spray jetsthereby ensuring a continuous and distributed or spread spraying of themixture. Said mixture necessarily passes through the ionizing fieldcreated by the stretched metallic currentcarrying wire 26. Beyond theionizing field, the particles of powdered product which are subjected toan electrostatic charge are sprayed or projected onto the parts whichare conveyed through the cabin 1. When the distributor 18 is relativelyhigh, the mixture must be brought to sufficient pressure to ensure thatthe upper part of the distributor 18 is suitably fed with theairpowdered product mixture. To prevent the pressure causing formationof excessively strong spraying jets which would detach the particlessprayed onto the parts, the upper end of the distributor 18 is providedwith a relief flap 18, which returns the excess mixture to the cabin.

To prevent the excess powdered product escaping to the exterior of thecabin,. in spite of lock-chambers 2, the cabin 1 is connected by a pipe30 to a source of suction which ensures that the pressure inside thecabin is lower than the surrounding pressure. The result is that theexcess product is drawn out of the cabin and recovered through a cyclone(not shown) and recycled to the container 4. The pipe 30 is provided inthe upper part of cabin 1 so as to limit the amount of the excessproduct drawn out, the major part thereof falling to the lower part ofthe cabin 1, where it is collected by the recovering means 7 anddirected toward the supply tank.

The parts or structures which are made to travel through the cabin lhave, of course, an electrostatic charge which is different from thecharge of the sprayed particles of the powdered product so that theparts are automatically covered with an adhering coat. Said coat is thensubmitted, out of the spraying zone or possibly outside the cabin 1, toa fixing treatment so as to obtain an homogeneous, dense and resistantcoating.

With this arrangement of the spraying device, there is no risk ofemanation, evaporation or spraying of the treating or coating productoutside the cabin, and the consumption of said product is limited to thequantity required to ensure a complete and even coating of the partswhich can be conveyed, with no loss or flow of the product, to a stationoutside the cabin 1 to receive the fixing treatment.

FIG. 3 shows that the spraying device may have more than one spraydistributor when opposed surfaces of parts have to be coated or treated.According to FIG. 3, the container 4 supports two metering and mixingmeans 9a,9b, placed in a staggered manner. The means 9a,9b, communicatewith individual pipes 16a,16b supplying compressed air and alsocommunicate with two tubes 17a,17b leading to two spray distributors18a,18b. The wires 26a,26b of said distributors can be supplied withcurrent by two different generators or by a generator 31 having twooutputs. The shutters 13a,13b are connected to control rods l4a,l4bpreferably accessible simultaneously from one of the sides of cabin l.The two spray distributors 18a,l8b can have a similar or differentshape, depending on the characteristics of the exposed surfaces of theparts to be treated.

FIG. 4 shows a modification in which the spray'distributor 18 iscomposed of a tubular element 32 made of an insulating material anddefining an axial slot 33. The tubular element 32 contains a dividingcomponent 34 shaped like a comb having teeth 35 which have differentlengths but ends aligned in a plane parallel to the plane of the opposedlongitudinal edge of the component 34. The latter is placed in the slot33 in such manner that the shorter teeth are located adjacent the baseof tubular element 32. The purpose of this arrangement is to ensure thatthe jets of the mixture passing through the slot 33 have a substantiallyuniform concentration all along the distributor 18. Indeed, the spaced36 between the teeth ensure a deviation of the product into the slot 33which progressively increases with increase in the length of the teeth35 and this compensates for the reduction in the concentration of theair-powder mixture as it rises in the distributor 18. This allows thesame quantity of powder to be sprayed throughout the height of the spraysheet formed by the aligned jets.

If the dividing component 34 is made of an insulating material, the wire16 has to be connected to the high frequency electric power generator29. However, the component 34 can be made of an electrically conductivematerial and connected to the generator 29 by conductors 37 and 38. Thecomponent 34 may have a width which is different from the section of thedistributor 18 so as to dispose the ends of the teeth 35 on either sideof the slot 33.

A further modification is represented in FIG. 5 according to which thedividing component is composed of a strip or a filament 39 havingcorrugations 40 whose magnitudes increase from the end 41 located in thelower part of the distributor 18. The corrugations 40 are so designed asto have a configuration whose transverse extent is equivalent to that ofthe spaces 36 between teeth 35 so that they perform the same functionwhen the filament of the strip 39 is disposed in the distributor 18 insuch manner that the aligned crests of the corrugations 40 are at leastpartly engaged within the axial slot 33. The strip or filament 39 can bemade of insulating material when the electrostatic field is produced bythe wire 26 or of an electrically conductive material in which case itis directly connected to conductors 37 and 38.

FIG. 6 shows another embodiment of the means for supplying andsubsequently recovering the powdered product. According to thisembodiment, cabin l includes a plane bottom 42 under which is hung,through elastic sealing elements 43 such as flat gaskets, a

hopper 44 constituting the recovering or recycling means for the excesspowdered product. The bottom of hopper 44 is extended by a nozzle orother tubular element 45 the interior of which is provided with aremovable filtering cartridge 46. The above-described recovering meansis connected to a vibrator 47 of any suitable type. The nozzle isconnected through a flexible sleeve 48 to a tubular shaft 49 projectingfrom above a container or tank 50. A horizontal metering and mixingmeans 51 extends through the tank 50 and is connected, on one hand, tothe tube 17 and, on the other hand, to the air-injection pipe 16. Themeans 51 can be directly constituted by the end portion of the tube 17into which the pipe 16 partly extends. Preferably, the means 51 isconstituted by a sleeve slidably mounted on the tube 17 so that by theadjustment of the axial position of the sleeve through a manual control,it is possible to vary the proportion of the drawn-in powdered productwithout modifying the volume of the carrier fluid supplied by the pipe16.

The metering and mixing means 51 is placed above a porous element 52dividing the tank. into a lower chamber 53 and an upper chamber 54. Thechamber 53 communicates with a pipe 55 supplying air at low pressure,whilst the chamber 54 contains the powdered product, it being filledwith the product through an inspection hole 56. The chamber 54 alsoincludes a float 57, operating a switch 58 controlling the electriccurrent 59 supplied to the vibrator.

The device of FIG. 6 operates in the following manner:

First, when starting the device, the lower chamber 53 of the tank 50 issupplied with air after having previously filled the chamber 54 with asuitable quantity of powdered product. The air delivered by pipe 55passes through the porous element 52 and ensures that the powderedproduct is put in suspension in the air. Thus, the behavior of theproduct can be likened to that of a fluid or liquid having a practicallystable level. The float 57 is consequently kept in its upper positionand the switch 58 cuts off the supply to the vibrator 47. The pipe 16 issupplied with the air as described above so as to supply theair-powdered product mixture to the spray distributors, the metering'andmixing means 51 being adjusted if required.

As, in the previously describe embodiment, the excess powdered productfalls by gravity onto the bottom 42 and the hopper 44 while being keptat the level of this recovering or recycling element by the presence ofi the filtering cartridge 46. When the consumption of the powderedproduct causes the level of tank 50 to drop below the point ensuring agood operation of the metering and mixing means 51, the float 57 isurged downwardly and closes the switch 58 which allows power to besupplied to the vibrator 47.

The vibrations of the vibrator 47 are transmitted to the recoveringmeans which causes the excess powdered product to fall into the tank 50and thus reestablishes the optimum level of the product in the tank.

It must be understood that the recycling of the excess product which iscollected by the recovering means and also possibly by a cyclone placedin the suction pipe 30, must be compensated from time to time by acomplementary filling of the tank 50 when the level of the charge ofproduct in this tank does not permit optimum operation of the meteringand mixing means 51.

It was mentioned hereinbefore that, for the purpose of preventing thepresence of excessively strong jets in the lower part of the distributor18, a pressure relief flap l8, is provided. Another solution consists inthe provision of a baffle-plate in an adjustable position in front ofthe slot 20 to ensure the deviation of a variable fraction of each jetas it issues from the distributor. The distributor can also beadvantageously inclined so as to prevent droppings from the upper jetscausing an increased concentration of product in the lower jets.

lclaim:

1. A device for spraying an electrified powdered coating or treatingmaterial onto the surface of a structure, comprising a cabin havingopposed walls, means for conveying and supporting said structure in apath in the cabin, means defining apertures in said opposed walls forthe passage of said conveying and supporting means and said structure,means for maintaining the interior of the cabin at a pressure lower thana pressure prevailing outside the cabin, spray distributing meanslocated in the cabin for spraying onto said structure supported in saidpath a mixture of air and said powdered material, means for creating adifference of electrostatic charge between said powdered material ofsaid mixture and said structure, the spray distributing means comprisingat least one hollow element, spray outlet means in form of alongitudinally extending slot in the hollow element, means for'dividingsaid mixture issuing from said outlet means into a plurality of sprayjets, said dividing means comprising an element which extends fromwithin the hollow element into said slot and defining, with said outletmeans, orifices producing jets of said mixture, a powdered material tankadjacent a lower part of the cabin, adjustable means for metering theamount of powdered material taken from the tank and mixing the materialwith air,-said adjustable means for metering and mixing the powderedmaterial comprising means defining a cavity having an inlet disposed inthe tank for receiving the powdered material in the tank, a compressedair supply pipe for connection to a source of air under pressure forsupplying air to said cavity and means for putting said cavity incommunication with the hollow element of the spray distributing means,and means for recovering excess powdered material which has not becomedeposited on said structure, said recovering means being capable ofguiding back said excess powdered material into the tank.

2. A device as claimed in claim 1, wherein said means for putting saidcavity in communication with the hollow element comprises a tube forhomogenizing said mixture.

3. A device as claimed in claim 1, wherein the spray outlet meanscomprise means defining an elongate opening in the hollow element andthe dividing means comprise a strip located in said opening and havingtwo opposed faces and notches in said opposed faces, the notches in eachof said opposed faces being spaced equal distances apart from each otherand the notches of one of said opposed faces being in staggered relationto the notches of the other of said opposed faces, said notches definingwith said opening outlets producing said spray jets.

4. A device as claimed in claim 1, wherein the spray outlet meanscomprise means defining an upwardly extending elongate opening in thehollow element and the dividing means comprise an upwardly extendingstrip located in said opening and having a plurality of transverselyextending teeth which define a plurality of gaps which progressivelyincrease in length from one gap to another in the direction upwardly ofthe strip, said teeth having outer ends substantially parallel with saidelongate opening.

5. A device as claimed in claim 1, wherein the spray outlet meanscomprise means defining an upwardly extending elongate opening in thehollow element and the dividing means comprise an elongate member havingtransversely extending loop portions defining transverse corrugationswhich progressevely increase in transverse extent from one corrugationto another in the direction upwardly of the member, said corrugationshaving outer end portions substantially parallel with said elongateopenings.

6. A device as claimed in claim 1, wherein the means for creating adifference of electrostatic charge comprise a wire extending in front ofthe spray outlet means and a high-frequency current generator connectedto said wire.

7. A device as claimed in claim 1, wherein the means for creating adifference of electrostatic charge comprise said means for dividing saidmixture which is in the form of an electrically conductive elementextending in the spray outlet means and a high-frequency currentgenerator connected to the conductive element.

8. A device as claimed in claim 1, wherein the metering and mixing meanscomprise a tube having a small lower inlet portion adjacent and inspaced relation to a bottom wall of the tank and a large upper outletend portion, an adjustable shutter associated with the tube for variablyclosing the outlet end portion, the tube defining said cavity and saidcavity communicating with the hollow element in a region intermediatesaid end portions of the tube.

9. A device as claimed in claim 1, wherein the tank is disposed belowthe cabin and a passageway connects the tank to the recovering meanswhich are vibratory.

10. A device as claimed in claim 9, wherein the recovering meanscomprise a hopper located at the base of the cabin, resilientlyyieldable means connecting the hopper to a lower part of the cabin andallowing vibration of the hopper relative to the cabin, and vibratingmeans associated with the hopper for vibratin the ho er, said assa ewabein flexible.

fil. A d ice as cl imef in clii- 1m 1 further comprising a porous walldividing the tank into an upper chamber for containing said powderedmaterial and a lower chamber, a pipe for connection to a low-pressureair supply connected to the lower chamber for fluidifying the powderedmaterial in the upper chamber via said porous wall, float means in theupper chamber responsive to the level of the powdered material in theupper chamber and associated with the vibrating means to controloperation of the vibrating means in accordance with the level of thepowdered material in the upper chamber.

1. A device for spraying an electrified powdered coating or treatingmaterial onto the surface of a structure, comprising a cabin havingopposed walls, means for conveying and supporting said structure in apath in the cabin, means defining apertures in said opposed walls forthe passage of said conveying and supporting means and said structure,means for maintaining the interior of the cabin at a pressure lower thana pressure prevailing outside the cabin, spray distributing meanslocated in the cabin for spraying onto said structure supported in saidpath a mixture of air and said powdered material, means for Creating adifference of electrostatic charge between said powdered material ofsaid mixture and said structure, the spray distributing means comprisingat least one hollow element, spray outlet means in form of alongitudinally extending slot in the hollow element, means for dividingsaid mixture issuing from said outlet means into a plurality of sprayjets, said dividing means comprising an element which extends fromwithin the hollow element into said slot and defining, with said outletmeans, orifices producing jets of said mixture, a powdered material tankadjacent a lower part of the cabin, adjustable means for metering theamount of powdered material taken from the tank and mixing the materialwith air, said adjustable means for metering and mixing the powderedmaterial comprising means defining a cavity having an inlet disposed inthe tank for receiving the powdered material in the tank, a compressedair supply pipe for connection to a source of air under pressure forsupplying air to said cavity and means for putting said cavity incommunication with the hollow element of the spray distributing means,and means for recovering excess powdered material which has not becomedeposited on said structure, said recovering means being capable ofguiding back said excess powdered material into the tank.
 1. A devicefor spraying an electrified powdered coating or treating material ontothe surface of a structure, comprising a cabin having opposed walls,means for conveying and supporting said structure in a path in thecabin, means defining apertures in said opposed walls for the passage ofsaid conveying and supporting means and said structure, means formaintaining the interior of the cabin at a pressure lower than apressure prevailing outside the cabin, spray distributing means locatedin the cabin for spraying onto said structure supported in said path amixture of air and said powdered material, means for Creating adifference of electrostatic charge between said powdered material ofsaid mixture and said structure, the spray distributing means comprisingat least one hollow element, spray outlet means in form of alongitudinally extending slot in the hollow element, means for dividingsaid mixture issuing from said outlet means into a plurality of sprayjets, said dividing means comprising an element which extends fromwithin the hollow element into said slot and defining, with said outletmeans, orifices producing jets of said mixture, a powdered material tankadjacent a lower part of the cabin, adjustable means for metering theamount of powdered material taken from the tank and mixing the materialwith air, said adjustable means for metering and mixing the powderedmaterial comprising means defining a cavity having an inlet disposed inthe tank for receiving the powdered material in the tank, a compressedair supply pipe for connection to a source of air under pressure forsupplying air to said cavity and means for putting said cavity incommunication with the hollow element of the spray distributing means,and means for recovering excess powdered material which has not becomedeposited on said structure, said recovering means being capable ofguiding back said excess powdered material into the tank.
 2. A device asclaimed in claim 1, wherein said means for putting said cavity incommunication with the hollow element comprises a tube for homogenizingsaid mixture.
 3. A device as claimed in claim 1, wherein the sprayoutlet means comprise means defining an elongate opening in the hollowelement and the dividing means comprise a strip located in said openingand having two opposed faces and notches in said opposed faces, thenotches in each of said opposed faces being spaced equal distances apartfrom each other and the notches of one of said opposed faces being instaggered relation to the notches of the other of said opposed faces,said notches defining with said opening outlets producing said sprayjets.
 4. A device as claimed in claim 1, wherein the spray outlet meanscomprise means defining an upwardly extending elongate opening in thehollow element and the dividing means comprise an upwardly extendingstrip located in said opening and having a plurality of transverselyextending teeth which define a plurality of gaps which progressivelyincrease in length from one gap to another in the direction upwardly ofthe strip, said teeth having outer ends substantially parallel with saidelongate opening.
 5. A device as claimed in claim 1, wherein the sprayoutlet means comprise means defining an upwardly extending elongateopening in the hollow element and the dividing means comprise anelongate member having transversely extending loop portions definingtransverse corrugations which progressevely increase in transverseextent from one corrugation to another in the direction upwardly of themember, said corrugations having outer end portions substantiallyparallel with said elongate openings.
 6. A device as claimed in claim 1,wherein the means for creating a difference of electrostatic chargecomprise a wire extending in front of the spray outlet means and ahigh-frequency current generator connected to said wire.
 7. A device asclaimed in claim 1, wherein the means for creating a difference ofelectrostatic charge comprise said means for dividing said mixture whichis in the form of an electrically conductive element extending in thespray outlet means and a high-frequency current generator connected tothe conductive element.
 8. A device as claimed in claim 1, wherein themetering and mixing means comprise a tube having a small lower inletportion adjacent and in spaced relation to a bottom wall of the tank anda large upper outlet end portion, an adjustable shutter associated withthe tube for variably closing the outlet end portion, the tube definingsaid cavity and said cavity communicating with the hollow element in aregion intermediate said end portionS of the tube.
 9. A device asclaimed in claim 1, wherein the tank is disposed below the cabin and apassageway connects the tank to the recovering means which arevibratory.
 10. A device as claimed in claim 9, wherein the recoveringmeans comprise a hopper located at the base of the cabin, resilientlyyieldable means connecting the hopper to a lower part of the cabin andallowing vibration of the hopper relative to the cabin, and vibratingmeans associated with the hopper for vibrating the hopper, saidpassageway being flexible.